This invention relates to injection of pressurized materials through a distribution system, such as injection molding of plastic melt in a hot runner system. More specifically, this invention relates to an improved injection molding hot runner system in which a single controller controls the rate of melt flow through two or more gates.
U.S. Pat. No. 5,556,582 discloses a multi-gate single cavity system in which the rate of melt flow through the individual gates is controlled independently via a control system according to specific target process conditions. This system enables the weld line of the part (the section of the part in which the melt from one gate meets the melt from another gate) to be selectively located. It also enables the shape of the weld line to be altered to form a stronger bond.
The ""582 patent discloses controlling the rate of melt flow with a tapered valve pin at the gate to the mold cavity. It also discloses placing a pressure transducer inside the mold cavity. Placing the pressure transducer inside the mold cavity can result in the pressure transducer sensing pressure spikes which can occur when the valve pin is closed. A pressure spike sensed by the transducer can cause an unintended response from the control system, and result in a less precise control of the melt flow than desired.
The control system disclosed in the ""582 patent uses the variables of valve pin position and cavity pressure to determine what position the valve pin should be in. Thus, the algorithm performed by the control system in the ""582 patent utilizes two variables to control the rate of melt flow into the cavity.
An injection molding system comprising a manifold for distributing material injected from said injection molding machine to first and second runners, wherein the first runner leads to first and second gates, and a controller to control the rate of material flow though the first runner, independently of the second runner.
A distribution system for distributing melt flow comprising a first runner that comprises a plurality of distribution nozzles, a second runner comprising at least one distribution nozzle and a controller capable of controlling the material flow to the first runner independently of the second runner.
A method of injection molding, comprising feeding a material to a manifold, feeding the material from the manifold to a runner that leads to first and second gates and controlling material flow at a point in the first runner to thereby control the rate of material flow through the first and second gates.
An injection molding system comprising a manifold for distributing material to a runner, a plurality of gates coupled to the runner, and a controller positioned in the runner to control the flow of material to the plurality of gates.